1. Field of the Invention
This invention relates to gas turbine engines, and more particularly to a seal means extending about the interior of the outer case of such an engine.
2. Description of the Prior Art
A gas turbine engine has a compression section, a combustion section and a turbine section. The turbine section has a rotor assembly and a stator assembly. An annular flowpath for working medium gases extends axially through the engine. The annular flowpath passes in alternating succession between components in the rotor assembly and components in the stator assembly. Components of the stator, including an outer case, circumscribe the annular flowpath. A flowpath for cooling air extends axially through the engine between the outer case and the flowpath for working medium gases.
In modern engines, the cooling air is flowed through passages on the interior of the case. The cooling air removes heat from the case and from turbine components such as vanes in intimate contact with the hot working medium gases. Along the cooling air flowpath, the cooling air is at a higher pressure than the surrounding gases. The case forms the outer boundary of the cooling air flowpath. An upstream boundary and a downstream boundary are formed in part by structure adjacent to the case and positioned by the case. A seal means extends between the adjacent structure to form an inner boundary of the flowpath.
In U.S. Pat. No. 3,992,126 to Brown et al., entitled "Turbine Cooling", an annular air cavity is formed between a circumferentially extending ring and the outer case. The upstream end of the ring opposes an outwardly facing surface on an upstream flange. A plurality of vane feet urge the upstream end of the ring into sealing contact with the upstream flange. The downstream end of the ring opposes an inwardly facing surface on a downstream flange and is securely attached to the downstream flange by bolts.
Notwithstanding the above art, scientists and engineers are still seeking to increase the sealing effectiveness of a seal means extending about the interior of an engine case between adjacent structures positioned by the engine case.